The invention relates to a novel skin friendly antiperspirant composition in which the modifying component comprises a polyhydric alcohol, preferably glycerin, is substantially complexed within the antiperspirant. The invention is applicable to the types of activated or nonactivated aluminum or aluminum/zirconium salts that are commonly considered antiperspirant active materials and are covered by FDA OTC Tentative Final Monograph as Category I.
It is desirable for an antiperspirant product to provide aesthetics (pleasing skin feel) in addition to excellent antiperspirancy. Appearance and feel of the skin is a major concern to the consumer as well as to the cosmetic industry. In order to understand how to control skin feel and appearance it is necessary to gain a better understanding of biological/biophysical factors affecting stratum corneum (SC), the outermost layer of the skin.
The structure and function of the stratum corneum has been the subject of intensive investigation over the past three decades. Its structure in the published literature of L. D. Rheim, etal, xe2x80x9cDevelopment of Stratum Corneum Lipid Model to Study the Cutaneous Moisture Barrier Propertiesxe2x80x9d Colloids and Surfaces, 48 (1990) 1-11 Elseiver Science Publishers, has been likened to brick wall, with the bricks representing corneocytes themselves and the xe2x80x98mortarxe2x80x99 representing the highly specialized intercellular lipids. The intercellular lipids are composed primarily of ceramides, cholesterol and fatty acids together with smaller amounts of phospholipids and glucosylceramides. These lipids form the major permeability barrier to the loss of water from the underlying epidermis and also from the part of the intercellular cement which helps to maintain the integrity of the tissue.
Human stratum corneum contains 15 such corneocyte/lipid layers. The corneocytes contain mainly the structural protein keratin.
A major function of the stratum corneum is to provide a barrier to evaporation of water. If this layer is removed from the skin e.g., by tape stripping, a fifty (50) fold increase in the rate of water loss ensues. Moisturization capacity of the SC is a major concern to the cosmetic industry since consumers are highly concerned about dry skin and moisture replenishment. Additionally dry skin can result in increased incidence of cuts during shaving.
The intercellular lipids are thought to play a major role in preventing water loss through the stratum corneum. To better understand the barrier function of the intercellular lipids and their role in regulating moisture loss from skin, numerous researchers are probing the structural organization of stratum corneum lipids and trying to understand what is the mechanism through which polyols and especially glycerin, mediate its effect on alleviating skin xerosis in vivo.
It has been shown that glycerin does not exhibit humectant properties at or below 6% RH (relative humidity) that is, neat glycerin samples exposed to 6% RH did not gain water over time. Thus, in low relative humidity climates it is unlikely that glycerin improves dry skin by humectancy. Rheim, et al. found that by incorporating glycerin into lipid model (at 10% levels) it prevented the formation of solid crystals and maintained a largely liquid crystalline state for the lipid/glycerin system. It was therefore concluded that in dry atmosphere glycerin may act as a moisturizer by inhibiting the lipid phase transitions from liquid to solid crystals. Maintaining the lipid in a liquid crystalline state with only small amounts of solid crystals may be the key for optimal barrier function.
Using in vitro stratum corneum extensibility model, Rawling, et al (xe2x80x9cThe effect of glycerol and humidity on desmosome degradation in stratum corneumxe2x80x9d, Arch. Dermatol Res. 1995 287: 437-464) have consistently found glycerin to be superior to all other humectants and polyols in skin xerosis and their effect of inhibiting lipid crystallinity.
It has also been reported that enzymatic activity, and thereby desmosome degradation occurs only above a certain water content in the stratum corneum. When the stratum corneum lipid structure is disturbed, the resulting reduction in stratum corneum hydration leads to the retention of corneocytes on the skin""s surface and the manifestation of skin xerosis due to reduced desmosome degradation. If, therefore, stratum corneum moisturization and water barrier function can be restarted by the topical use of a suitable moisturizer, the desquamatory process can be restored by the topical use of an ideal moisturizer and xeratic skin conditions may be treated more effectively. One compound that meets all these requirements is glycerin. The action of glycerin has been explained in terms of its occlusive, humectant and lipid phase modulating properties, all of which translate into moisturization and barrier improvements for the stratum corneum. More recently, it has been shown that glycerin aids enzyme layers of desmosomes in the stratum corneum. All of this represents an alternate, more likely molecular mechanism of action for skin moisturizing by glycerin.
Glycerin is not the only material that has been shown to condition the skin without hydrating it. The effects of another nonhygroscopic skin softener, a modified triglyceride known as glyceridacid was reported by R. S. Summers, et al, xe2x80x9cThe effect of lipids, with and without humectant, on skin xerosis. J. Soc. Cosmetic Chemist Vol. 47; 27-39xe2x80x9d, as exerting skin softening effects via interaction with the stratum corneum lipids. Recently another class of compounds known as xcex1 hydroxyacids have been investigated and these compounds which, are non humectants have been found to plasticize the stratum corneum even under conditions of low relative humidity (20% RH). Fraebe, et al , xe2x80x9cPrevention of Stratum Corneum lipid phase transitions in vitro by glycerolxe2x80x94an alternative mechanism for skin moisturizationxe2x80x9d. J. Mattai, J. Soc. Cosmetic Chemist Vol. 41, 51-65 reported that xcex1 hydroxy acids, particularly the longer chains (C10, C12) species may enable these compounds to penetrate the fatty acid chains of the bilayer, interrupting the close packing of these chains and thereby enhancing the fluidity of the membrane.
As pointed out by P. Thau (xe2x80x9cGlycerin Current Insights into the Functional Properties of Classic Cosmetic Raw Materialxe2x80x9d, J. Cosmetic Sci. Vol. 53, 229-236xe2x80x9d) studies conducted within the past twenty to twenty five years have enabled us to gain significant understanding of the complex interactions of glycerin with the epidermis. Results of these studies in the form of interaction of glycerin with the epidermis are listed below.
1. increases the extensibility of the stratum corneum
2. increases the water gradient in the skin
3. reduces surface roughness (may not be caused solely by moisturization)
4. penetrates into the phospholipid bilayers
5. maintains the intercellular lipid cement in a fluid liquid crystal state, particularly under conditions of low temperature and low RH
6. accelerates recovery of barrier function in vivo
7. serves to accelerate wound healing
8. aids in the digestion of desmosomes
9. provides a skin protection function
10. enhances corneocyte desquamation
11. does not interfere with biochemical processes in the skin
The preservation of skin structure and function with concomittant mildness and metabolic inactivity truly makes glycerin the quintessential cosmetic ingredient. However, blending of glycerin with antiperspirant powder (basic aluminum halides, nitrate, or aluminum/zirconium complexes as identified in OTC monograph) in a typical antiperspirant stick formulation results in agglomeration and formation of gritty particles requiring use of flow enhancers such as silica and talc. In general, colloidal silica in amounts up to about 1% by weight by the total composition and preferably about 0.05 to 0.5% is used. However, silica and talc present dusting and health related problems and the finished product does not provide excellent skin feel as they tend to increase drag.
Besides health concerns in handling of silica and talc, the products also affect aesthetics of the finished stick; the product tends to have grittiness and leaves moderate white residue on the skin.
Therefore, it is an object of this invention to provide an antiperspirant active composition which when formulated into an antiperspirant stick has an improved combination of functional properties, including excellent antiperspirancy, skin conditioning and moisturizing.
It is another objective of this invention to provide an active which does not require the use of silica and talc as flow enhancers in the final formulation thus simplifying the formulation and manufacturing process.
It is yet another objective of this invention to provide an active which provides excellent skin feel (i.e., no grittiness).
It is yet another objective of this invention to maintain high antiperspirancy for the new product.
It is yet another objective of this invention to define the morphological parameters of the active powder which gives the desired properties.
It is yet another objective of this invention to provide improved color (whiteness) of the product.
The novel skin friendly antiperspirant of the invention in which a suitable polyhydric alcohol, e.g., glycerin, is complexed with the antiperspirant is formed with the type of activated or nonactivated aluminum or aluminum/zirconium salts that are commonly considered antiperspirant active materials and are covered by FDA OTC Tentative Final Monograph as Category I. Suitable antiperspirant salts include (but are not limited to): aluminum chlorohydrate, aluminum sesquichlorohydrate, aluminum chlorohydrex PG, aluminum dichlroohydrex PG, aluminum sesquichlorohydrex PG, aluminum chlorohydrex PEG, aluminum sesquichlorohydrex PEG, aluminum chloride (15 perecent or less aqueous solutions), aluminum zirconium chlorohydrates, aluminum zirconium trichlorohydrate, aluminum zirconium tetrachlorohydrate, aluminum zirconium pentachlorohydrate, aluminum zirconium octachlorohydrate, aluminum zirconium trichlorohydrex Glycine (Gly), aluminum zirconium penta chlorohydrex Gly, aluminum zirconium tetrachlorohydrex Gly, aluminum zirconium octachlorohydrex Gly, buffered aluminum sulfate, basic aluminum chlorides, zirconium hydroxychloride, zirconyl chloride, basic aluminum nitrates, basic aluminum chlorides combined with zirconyl oxychloride and/or hydroxychloride and organic complexes of each of basic aluminum chlorides with or without zirconyl chloride or zirconium hydroxychloride and mixture of any of the foregoing. Aluminum or aluminum and zirconium complexes having metals/anion ratio of 0.9:1 to 2.1:1 where an anion could be Cl, Br, I and/or NO3, with or without additives such as amino acids or polyhydric alcohols.
A particular group of such antiperspirant active includes various aluminum-zirconium-glycine salts with the formula:
AlnZr(OH)(3n+4xe2x88x92x)Yx(AA)q(R)p
wherein xe2x80x9cnxe2x80x9d is from 2.0 to 10.0; preferably from 3 to 8;
wherein xe2x80x9cxxe2x80x9d is from 1.4 to 12.3, calculated from metal to chloride ratio (M/Cl, 0.9:1-2.1:1); preferably from 2 to 8, wherein xe2x80x9cYxe2x80x9d is Cl, Br, I and/or NO3;
wherein xe2x80x9cqxe2x80x9d is from 0.5 to 3.0, preferably from 1 to 2; and AA is an amino acid, and wherein xe2x80x9cRxe2x80x9d is an organic solvent having at least two carbon atoms and at least one hydroxy group and xe2x80x9cpxe2x80x9d has a value of from zero to 1.5
and basic aluminum chlorides with the formula:
Al2(OH)6xe2x88x92x1Yx1(R)p
wherein Y is Cl, Br, I and/or NO3 and x1 is greater than zero and less than or equal to six (i.e. 0 less than x1xe2x89xa66).
The invention contemplates also those antiperspirant actives comprising aluminum and aluminum zirconium salts combined with zinc and/or tin, i.e. Al/Zr/Zn, Al/Zn, Al/Sn, Al/Zr/Sn, and the like,actives.
The polyhydric alcohol, which may be employed in preparing the skin friendly antiperspirant formulation of the invention may be selected from any of the suitable polyhydric and non-polyhydric alcohols which are generally used in cosmetic compositions and which are liquid at room temperature. These typically include liquid polyhydric alcohols having from 3 to 12 carbon atoms and three or more hydroxy groups such as, for example, glycerin, diglycerol, sorbitol, 1,2,4-butanetriol; 1,2,6-hexanetriol, etc. and mixtures thereof. Most preferred are glycerol and diglycerol. Nonpolyhydric alcohol compounds that may be used are glycol ether such as monoalkyl ethers or xcex1 hydroxy acids.
The primary aspect of the present invention is to provide an antiperspirant product that not only performs as a highly efficacious antiperspirant but further serves as moisturizer and plasticizer and minimizes skin irritation especially for people with sensitive skin. An ideal antiperspirant with these desirable features should minimize sweat secretion causing little or no irritation and without overdrying the skin or leaving it taut after sustained use of antiperspirant or dry deodorants.
In accordance with the method of present invention an aqueous basic aluminum chloride solution or an aqueous basic aluminum chloride solution with an organic solvent such as propylene glycol, dipropylene glycol, tripropylene glycol, and the like as represented by the general formula:
Al2(OH)6xe2x88x92x1,Yx1(R)p
wherein Y is Cl, Br, I and/or NO3 and x1 is greater than zero and less than or equal to six (i.e. 0 less than x1xe2x89xa66) wherein xe2x80x9cRxe2x80x9d is an organic solvent having at least two carbon atoms and at least one hydroxy group and xe2x80x9cpxe2x80x9d has a value of from zero to 1.5, is mixed with glycerin at room temperature to about 105xc2x0 C., may be refluxed for 30 minutes to about 4 hrs.; is cooled to room temperature and mixed with zirconium hydroxy chloride glycinate solution having Cl/Zr atomic ratio of (0.8:1 to 2:1) and which has been refluxed to 2 hrs. The resultant solution is allowed to react at least for 30 minutes and is then filtered to obtain slightly amber to colorless solution. This solution is then dried by a suitable conventional means (viz spray dryer, vacuum dryer, oven dryer, tray dryer, freeze dryer, etc.) to yield a homogeneous skin friendly composition having the desired characteristics.
In the method of the present invention, glycerin may be added to zirconium hydroxy glycinate solution before, during or after the refluxing step or it may be added after zirconium hydroxy glycinate solution has been added to basic aluminum chloride and just before the spray drying at room temperature or at temperature up to 100xc2x0 C. Alternatively some of the glycerin may be added to basic aluminum chloride and the remainder to zirconium hydroxy glycinate solution.
The antiperspirant product of the invention comprises a novel complex composition in which part of the contained polyhydric alcohol, for example, glycerin, is complexed with the aluminum zirconium antiperspirant. It is postulated that approximately 20% to 70% of the glycerin is coordinated for aluminum zirconium antiperspirant complexes having Al/Zr atomic ratio of 2 to 10 and metals/anion ratio of 0.8 to 2.1:1; for basic aluminum chloride it appears to be less than 2% and the rest of the glycerin exists as a xe2x80x9cfreexe2x80x9d glycerin. The amount of glycerin present as complexed depends upon the type of antiperspirant active, total concentration of glycerin and at what step of the reaction process it is added. Free glycerin means it can be titrated quantitatively by the standard analytical method. However, some evidence demonstrates that at least part of this xe2x80x9cfreexe2x80x9d glycerin is absorbed and held at the surface of the complex. The combination of the presence of coordinated glycerin plus the presence of free glycerin appears to offer unique properties when formulated into an antiperspirant stick form and applied to human skin.
The coordination of glycerin molecule with aluminum-zirconium antiperspirant is demonstrated firstly by the chemical shift change (1H NMR) and the broadening of the chemical shift of the glycerin peak(s); and secondly by the titration of the glycerin molecule in the aluminum-zirconium-glycerin antiperspirant.
A new broad signal at xcx9c3.7 ppm was observed when 1H NMR was run on the aluminum-zirconium-glycerin antiperspirant, which is different from the three sharp multiple signals demonstrated by the glycerin molecule. This is an indication of the formation of a new interaction between the antiperspirant active and the glycerin molecule. Further, it has been discovered by the present invention that the complexation occurs between zirconium and glycerin.
In order to determine whether the polyhydric alcohol is complexed with aluminum to provide the composition of the invention or is not complexed, comparative experiments were run in which basic aluminum chloride solution (Reach 301, a product of Reheis Inc) was refluxed with glycerin for 4 hrs. and spray dried. The resultant powder was analyzed and the glycerin value that was titrated quantitatively by the standard analytical method was compared against the glycerin value determined based on the total carbon analysis. Results are shown below.
While not being bound by any theories it appears that if any glycerin is complexed with basic aluminum chloride it is appreciably less than the amount of glycerin complexed with an aluminum zirconium salt.
When chemical analysis was performed to calculate the glycerin value in aluminum-zirconium-glycerin antiperspirant, zirconium was first precipitated out because of the interference. Glycerin was found to be present in the zirconium precipitates. Further, it has been found that the value of glycerin by analytical titration is always less than the glycerin value calculated from total carbon analysis. The difference has been found to be the function of the type of antiperspirant, glycerin concentration and the process employed for making the product. The results indicate that glycerin is coordinated with the zirconium metal in the antiperspirant. Further there is less than 2% difference in the glycerin values in the aluminum-glycerin antiperspirant between chemical analysis by titration method and based on total analysis, providing additional indication that most of the glycerin is coordinated with zirconium. Also, 1H NMR of aluminum zirconium antiperspirant indicate chemical shift change and the broadening of the glycerin peaks due to complexation.
The antiperspirant salts which may be employed in preparing the novel complex of the invention include (but are not limited to) the following five groups:
A first group of such antiperspirant actives materials includes aluminum chlorohydrate, aluminum dichlorohydrate, aluminum sesquichlorohydrate, aluminum zirconium trichlorohydrate, aluminum zirconium tetrachlorohydrate, aluminum zirconium pentachlorohydrate, aluminum zirconium octachlorohydrate, aluminum zirconium trichlorohydrex glycine (gly), aluminum zirconium tetrachlorohydrex gly, and aluminum zirconium pentachlorohydrex gly and aluminum zirconium octachlorohydrex gly.
A second particular group of such antiperspirant actives include, by way of example (and not of a limiting nature), aluminum chlorohydrate, aluminum chloride, aluminum sesquichlorohydrate, zirconyl hydroxychloride, aluminum-zirconium glycine complex (for example, aluminum zirconium trichlorohydrx gly, aluminum zirconium octachlorohydrex gly), aluminum chlorohydrex PG, aluminum chlorohydrex PEG, aluminum dichlorohydrex PG, and aluminum dichlorohydrex PEG. Aluminum zirconium trichlorohydrex PG, aluminum zirconium tetrachlorohydrex PG complex, etc. Aluminum zirconium complexes having Al/Zr atomic ratio of 2:1 to 10:1 and metals to anion ratio of 0.9:1 to 2.1:1 and organic complexes thereof.
A third group of such antiperspirant include basic aluminum chlorides represented by the formula Al2(OH)6xe2x88x92x1Yx1 [wherein Y is Cl, Br, I and/or NO3 and 0 less than x1xe2x89xa66] with or without zirconyl oxychlorides and hydroxy chlorides and mixtures of any of the foregoing.
A fourth particular group of such antiperspirant actives include the enhanced efficacy aluminum salts and the enhanced efficacy aluminum/zirconium salt-glycine materials, having enhanced efficacy due to improved molecular distribution, known in the art and discussed, for example in U.S. Pat. Nos. 4,359,456, 4,775,528, 5,718,876, 5,908,616 and EP Patents 0,191,628, 0,256,832.
A fifth group of such antiperspirant actives includes salts of aluminum and tin, or tin zirconium and aluminum or aluminum, zinc and zirconium, with or without such additives as amino acids or polyhydric alcohols and combinations thereof.